Sheet conveyance device and image forming apparatus therefor

ABSTRACT

A sheet conveyance device includes a pair of conveyance rollers, a contact-release mechanism, an alignment mechanism, and a control portion. The contact-release mechanism moves first and second conveyance rollers, constituting the pair of conveyance rollers, into contact with and away from each other. The alignment mechanism aligns a sheet conveyed along the sheet conveyance passage in a sheet width direction. The alignment mechanism includes a pair of alignment members movable toward and away from each other in the sheet width direction and aligning the sheet in the sheet width direction by making contact, from both sides in the sheet width direction, with side edges of the sheet. The control portion controls the contact-release mechanism to move the first and second conveyance rollers away from each other, and aligns the sheet with the pair of alignment members located opposite each other in the sheet width direction.

INCORPORATION BY REFERENCE

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2021-117618 filed on Jul. 16, 2021, the contents of which are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a sheet conveyance device and to an image forming apparatus.

Sheet conveyance devices are known that perform skew correction for correcting a skew of a sheet conveyed along a sheet conveyance passage with respect to the sheet conveyance direction and displacement correction for correcting a displacement of the sheet in the sheet width direction orthogonal to the sheet conveyance direction.

SUMMARY

According to one aspect of the present disclosure, a sheet conveyance device includes a pair of conveyance rollers, a contact-release mechanism, an alignment mechanism, and a control portion. The pair of conveyance rollers conveys a sheet along a sheet conveyance passage. The contact-release mechanism moves a first and a second conveyance roller, constituting the pair of conveyance rollers, into contact with and away from each other. The alignment mechanism aligns the sheet conveyed along the sheet conveyance passage at a predetermined alignment position in a sheet width direction orthogonal to a sheet conveyance direction. The control portion controls the pair of conveyance rollers, the contact-release mechanism, and the alignment mechanism. The alignment mechanism includes a pair of alignment members movable toward and away from each other in the sheet width direction. The alignment members align the sheet in the sheet width direction by making contact, from both sides in the sheet width direction, with side edges of the sheet conveyed along the sheet conveyance passage. The control portion controls the contact-release mechanism to move the first and second conveyance rollers away from each other, and aligns the sheet with the pair of alignment members, which are located opposite each other in the sheet width direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional front view of an inkjet recording apparatus according to a first embodiment of the present disclosure;

FIG. 2 is a block diagram showing the configuration of the inkjet recording apparatus in FIG. 1 ;

FIG. 3 is a top view around an alignment mechanism in a sheet conveyance device in the inkjet recording apparatus in FIG. 1 ;

FIG. 4 is a top view of the alignment mechanism in the sheet conveyance device in FIG. 3 ;

FIG. 5 is a front view of the alignment mechanism in the sheet conveyance device in FIG. 3 ;

FIG. 6 is a side view of the alignment mechanism in the sheet conveyance device in FIG. 3 ;

FIG. 7 is a schematic side view around the alignment mechanism in FIG. 6 , showing a state before a sheet is aligned;

FIG. 8 is a schematic side view around the alignment mechanism in FIG. 6 , showing a state where a pair of alignment members are in contact with the sheet and a pair of conveyance rollers are apart from each other;

FIG. 9 is a schematic side view around the alignment mechanism in FIG. 6 , showing a state where the pair of conveyance rollers are in contact with each other with the sheet nipped between them and the sheet is held at the nip;

FIG. 10 is a schematic side view around the alignment mechanism in FIG. 6 , showing a state where the pair of alignment members are in contact with the sheet when a sheet pressing member is used;

FIG. 11 is a schematic side view around the alignment mechanism in FIG. 6 , showing a state Where the sheet is in contact with the sheet pressing member;

FIG. 12 is a schematic side view around the alignment mechanism in FIG. 6 , showing a state where only an other-side alignment member out of the pair of alignment members is apart from the sheet;

FIG. 13 is a schematic side view around the alignment mechanism in FIG. 6 , showing a state where pressing of the sheet by the sheet pressing member is canceled;

FIG. 14 is a top view around an alignment mechanism in a sheet conveyance device in an inkjet recording apparatus according to a second embodiment of the present disclosure;

FIG. 15 is a schematic sectional front view of an inkjet recording apparatus according to a third embodiment of the present disclosure; and

FIG. 16 is a diagram showing the timing of sheet conveyance and alignment on the inkjet recording apparatus in FIG. 15 .

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to the following contents.

FIG. 1 is a schematic sectional view of an inkjet recording apparatus 1 according to a first embodiment. FIG. 2 is a top view around a recording portion 5 of the inkjet recording apparatus 1 in FIG. 1 . In the present disclosure, the inkjet recording apparatus 1 is taken and described as one example of an image forming apparatus. The inkjet recording apparatus (image forming apparatus) 1 is, for example, a printer of an inkjet recording type. The inkjet recording apparatus 1 includes, as shown in FIG. 1 and FIG. 2 , an apparatus main body 2, a sheet feed portion 3, a sheet conveyance device 4, the recording portion 5, a drying portion 6, and a control portion 7.

The sheet feed portion 3 stores a plurality of sheets S and, during recording, separates and feeds out the sheets S one by one. The sheet conveyance device 4 conveys a sheet S fed out from the sheet feed portion 3 to the recording portion 5 and the drying portion 6 and then, after recording and drying, discharges the sheet S to a sheet discharge portion 21. When duplex recording is performed, the sheet conveyance device 4 makes a branch portion 43 distribute the sheet S having undergone recording and drying on the first side to a reversing conveyance portion 44 and then conveys the sheet S having its conveyance direction switched and its obverse and reverse sides reversed back to the recording portion 5 and the drying portion 6.

The sheet conveyance device 4 includes a first belt conveyance portion 41 and a second belt conveyance portion 42. The first belt conveyance portion 41 has a first conveyance belt 411 which is formed in an endless shape. The second belt conveyance portion 42 has a second conveyance belt 421 which is formed in an endless shape. The first and second belt conveyance portions 41 and 42 convey the sheet S in a state held by suction on the upper outer surfaces (upper surfaces) of the first and second conveyance belts 411 and 421. The first belt conveyance portion 41 is disposed below the recording portion 5 to convey the sheet S. The second belt conveyance portion 42 is located downstream of the first belt conveyance portion 41 in the sheet conveyance direction, and is disposed in the drying portion 6 to convey the sheet S.

The recording portion 5 is disposed opposite the conveying sheet S conveyed in a state held by suction on the upper surface of the first conveyance belt 411, above the first conveyance belt 411 at a predetermined interval from it. The recording portion 5 includes line inkjet recording heads corresponding to four colors, namely black, cyan, magenta, and yellow, respectively. The recording portion 5 discharges the ink from one after another of the recording heads corresponding to the four colors to the sheet S which is conveyed on the first conveyance belt 411 and records a full-color or monochrome image to the sheet S.

The drying portion 6 is disposed downstream of the recording portion 5 in the sheet conveyance direction and includes the second belt conveyance portion 42. In the recording portion 5 an ink image is recorded to the sheet S and the ink is dried in the drying portion 6 while the sheet S is being conveyed in a state held by suction on the first conveyance belt 421.

The control portion 7 includes a CPU, a storage portion, and other electronic circuits and components (none are illustrated). Based on the data and the control program stored in the storage portion, the CPU controls the operation of different components in the inkjet recording apparatus to perform processes related to the functions of the inkjet recording apparatus 1. The sheet feed portion 3, the sheet conveyance device 4, the recording portion 5, and the drying portion 6 receive commands from the control portion 7 individually and performs recording on the sheet S in coordination. The storage portion is composed of a combination of a nonvolatile storage device such as a program ROM (read-only memory), a data ROM, and the like and a volatile storage device such as a RAM (random-access memory).

The sheet conveyance device 4 includes a pair of conveyance rollers 4 r, a contact-release mechanism 8, and an alignment mechanism 9. The sheet conveyance device 4 includes a plurality of pairs of conveyance rollers on a sheet conveyance passage 45, including the pair of conveyance rollers 4 r disposed upstream of the recording portion 5 in the sheet conveyance direction. The contact-release mechanism 8 and the alignment mechanism 9 are disposed adjacent to the sheet conveyance passage 45 upstream of the recording portion 5 in the sheet conveyance direction.

Next, the construction around the alignment mechanism 9 in the sheet conveyance device 4 will be described with reference to FIGS. 1 and 2 as well as FIGS. 3, 4, 5, and 6 . FIG. 3 is a top view around the alignment mechanism 9 in the sheet conveyance device 4 in the inkjet recording apparatus 1 in FIG. 1 . FIGS. 4, 5, and 6 are a top view, a front view, and a side view, respectively, of the alignment mechanism 9 in the sheet conveyance device 4 in FIG. 3 . In FIG. 4 , a sheet pressing portion 93, which will be described later, is omitted from illustration.

In the following description related to the sheet conveyance device 4, the right-to-left direction along the left-right direction in FIGS. 3 and 5 , that is, the upward direction along the up-down direction in FIG. 4 , that is, the near-to-far direction along the depth direction with respect to the plane of FIG. 6 , is called the “sheet conveyance direction”, and is indicated by arrow Dc in FIG. 3 and the following figures. On the other hand, the “sheet width direction”, which is orthogonal to the sheet conveyance direction, is the up-down direction in FIG. 3 , that is, the left-right direction in FIGS. 4 and 6 , that is, the depth direction with respect to the plane of FIG. 5 , and is indicated by arrow Dw in FIG. 3 and the following figures.

The pair of conveyance rollers 4 r are composed of a first conveyance roller 4 a and a second conveyance roller 4 b which are disposed in the direction perpendicular to the conveyance surface for the sheet S in the sheet conveyance passage 45. For example, the first conveyance roller 4 a is a driving roller, and is rotated by a motor (not illustrated) and controlled by the control portion 7. For example, the second conveyance roller 4 b is a driven roller, and rotates by following the rotation of the first conveyance roller 4 a as a result of the circumferential surface of the second conveyance roller 4 b making contact with the circumferential surface of the first conveyance roller 4 a. The pair of conveyance rollers 4 r convey the sheet S in the sheet conveyance passage 45 while holding the sheet S at the conveyance nip portion formed by the first and second conveyance rollers 4 a and 4 b making contact with each other.

The contact-release mechanism 8 is disposed, for example, adjacent to the pair of conveyance rollers 4 r near the alignment mechanism 9. The contact-release mechanism 8 includes, for example, an urging member and a cam neither are illustrated). The urging member is configured as, for example, a compression spring and is coupled between a shaft 4 x of the second conveyance roller 4 b and a frame member of the apparatus main body 2. The urging member urges the shaft 4 x in the direction in which the second conveyance roller 4 b approaches the first conveyance roller 4 a.

The cam makes contact with, for example, the shaft 4 x of the second conveyance roller 4 b. The cam can rotate against the urging force of the urging member and move the shaft 4 x in the direction in which the second conveyance roller 4 b moves away from the first conveyance roller 4 a. Meanwhile, the second conveyance roller 4 b moves away from the sheet conveyance roller 4 a, for example, in the direction perpendicular to the conveyance surface for the sheet S in the sheet conveyance passage 45. In this way, the contact-release mechanism 8 moves the pair of conveyance rollers 4 r composed of the first and second conveyance rollers 4 a and 4 b towards and away from each other. The contact-release mechanism 8 is controlled by the control portion 7.

The alignment mechanism 9 includes a pair of alignment members 91, an alignment driving portion 92, and a sheet pressing portion 93.

The alignment mechanism 9 includes a pair of alignment members 91 along the sheet conveyance passage 45. In this embodiment, the alignment mechanism 9 includes two pairs of alignment members 91 along the sheet conveyance passage 45. Specifically, the alignment mechanism 9 includes a first pair of alignment members 91A and a second pair of alignment members 91B as the pair of alignment members 91. The first pair of alignment members 91A are disposed downstream in the sheet conveyance direction Dc, opposite each other in the sheet width direction Dw, and makes contact with the downstream side edge of the sheet S from both sides in the sheet width direction Dw. The second pair of alignment members 91B are disposed upstream in the sheet conveyance direction Dc, opposite each other in the sheet width direction Dw, and makes contact with the upstream side edge of the sheet S from both sides in the sheet width direction Dw.

The pair of alignment members 91 are disposed on the conveyance surface for the sheet S in the sheet conveyance passage 45. The pair of alignment members 91 are disposed at one side and the other side, respectively, in the sheet width direction Dw with respect to a middle portion of the sheet conveyance passage 45 in the sheet width direction Dw, opposite each other in the sheet width direction Dw. The pair of alignment members 91 include a one-side alignment member 91 r disposed at one side in the sheet width direction Dw and an other-side alignment member 91 f disposed at the other side. The one- and other-side alignment members 91 r and 91 f, disposed opposite each other in the sheet width direction Dw, have basically the same structure. Accordingly, unless necessary, the suffixes “r” and “f” for distinction may be omitted in the following description.

The pair of alignment members 91 each include an alignment portion 911 and a connection portion 912.

The alignment portion 911 is disposed above the conveyance surface of the sheet conveyance passage 45. The alignment portion 911 makes contact with the bottom face and the side edge of the sheet S conveyed along the sheet conveyance passage 45. The alignment portion 911 includes a side wall portion 911 a.

The side wall portion 911 a is disposed outward of the alignment portion 911 in the sheet width direction Dw. The side wall portion 911 a extends in the up-down direction and in the sheet conveyance direction Dc. The side wall portion 911 a makes contact with the side edge of the sheet S conveyed along the sheet conveyance passage 45. That is, the pair of alignment members 91 align the sheet S in the sheet width direction Dw by making contact with the side edge of the sheet S conveyed along the sheet conveyance passage 45 from both sides in the sheet width direction Dw. It is preferable that the side wall portion 911 a stick out inward in the sheet width direction Dw and have a projection or a curve of which a tip end part makes contact with the side edge of the sheet S.

The connection portion 912 is disposed below the alignment portion 911, below the conveyance surface of the sheet conveyance passage 45. The connection portion 912 connects to the alignment portion 911. The connection portion 912 is fixed to a belt 922, which will be described later, that is provided in the alignment driving portion 92 and that moves the pair of alignment members 91. By being driven by the alignment driving portion 92, the pair of alignment members 91 can reciprocate towards and away from each other in the sheet width direction Dw independently of each other.

As shown in FIGS. 4 and 5 , the alignment driving portion 92 is disposed below the conveyance surface of the sheet conveyance passage 45. The alignment driving portion 92 is provided one for each of the pair of alignment members 91. That is, in this embodiment, the sheet conveyance device 4 includes four alignment members 91, and thus includes four alignment driving portions 92. The alignment driving portions 92 are located at one and the other sides across the middle portion of the sheet conveyance passage 45 in the sheet width direction Dw. The alignment driving portions 92 each include a guide member 921, a belt 922, a pair of pullies 923, a driving motor 924, and an urging member 925. That is, the sheet conveyance device 4 includes a plurality of driving motors 924 and a plurality of urging members 925.

The guide member 921 has a rod-like shape extending in the sheet width direction Dw. The guide member 921 penetrates the connection portion 912 in the alignment members 91 in the sheet width direction Dw. The connection portion 912 can reciprocate in the extension direction of the guide member 921, that is, in the sheet width direction Dw.

The belt 922 is an endless belt formed in an oval shape along the sheet width direction Dw, parallel to the guide member 921. The belt 922 is wound around and supported by the pair of pullies 923. The belt 922 is rotated by the pair of pullies 923 and reciprocates the connection portion 912 in the alignment members 91 along the guide member 921 in the sheet width direction Dw.

The pair of pullies 923 are disposed side by side in the sheet width direction Dw. The pullies 923 are attached to the apparatus main body 2 rotatable about a rotation axis extending in the direction perpendicular to the conveyance surface for the sheet S in the sheet conveyance passage 45. One of the pair of pullies 923 is coupled to the driving motor 924 via a gear train and receives a rotative force from the driving motor 924. In this way, the pair of pullies 923 rotate the wound endless belt 922.

The driving motor 924 is connected to one of the pair of pullies 923 and rotates the pullies 923. The driving motor 924 is configured as, for example, a stepping motor. When the driving motor 924 is driven, the belt 922 rotates via the pullies 923 and the connection portion 912 in the alignment members 91 moves along the guide member 912 in the sheet width direction Dw. That is, the driving motor 924 moves the pair of alignment members 91 disposed opposite each other in the sheet width direction Dw independently of each other in the sheet width direction Dw. The alignment driving portion 92 can reciprocate the pair of alignment members 91 along the sheet width direction Dw by driving the driving motor 924.

The urging members 925 are configured as, for example, elastic members such as springs and, as shown in FIG. 4 , are disposed between the alignment members 91 and a support segment 2 a on the apparatus main body 2. The support segment 2 a is disposed in the middle of the sheet conveyance passage 45 in the sheet width direction Dw and supports one end portion of each urging member 925 in the alignment driving portions 92 in the sheet width direction Dw. The urging members 925 urge the pair of alignment members 91, which are disposed opposite each other in the sheet width direction Dw, independently along the direction moving away from the sheet S.

The alignment mechanism 9 thus aligns the sheet S conveyed along the sheet conveyance passage 45 at a predetermined alignment position in the sheet width direction Dw. The alignment driving portion 92 in the alignment mechanism 9 is controlled by the control portion 7.

Next, the operation of the contact-release mechanism 8 and the alignment mechanism 9 will be described with reference to FIGS. 7, 8, and 9 . FIG. 7 is a schematic side view around the alignment mechanism 9 in FIG. 6 , showing a state before the sheet S is aligned. FIG. 8 is a schematic side view around the alignment mechanism 9 in FIG. 6 , showing a state where the pair of alignment members 91 are in contact with the sheet S and the pair of conveyance rollers 4 r are apart from each other. FIG. 9 is a schematic side view around the alignment mechanism 9 in FIG. 6 , showing a state where the pair of conveyance rollers 4 r are in contact with each other with the sheet S nipped between them and the sheet S is held at the nip.

As shown in FIG. 7 , before the sheet S reaches the alignment mechanism 9, the pair of alignment members 91 are on standby in a state where the interval between them in the sheet width direction Dw is longer than the width of the sheet S. The width of the sheet S is set previously based on the size of the sheet S stored in the sheet feed portion 3.

When the sheet S reaches the alignment mechanism 9, the control portion 7 stops the rotation of the pair of conveyance rollers 4 r to stop conveying the sheet S. As shown in FIG. 8 , the control portion 7 controls the contact-release mechanism 8 to move away from each other the first and second conveyance rollers 4 a and 4 b constituting the pair of conveyance rollers 4 r near the alignment mechanism 9. The control portion 7 aligns the sheet S with the two pairs of alignment members 91. Specifically, for each of the pairs of alignment members 91 (the one- and other-side alignment members 91 r and 91 f) constituting the first and second pair of alignment members 91A and 91B, the control portion 7 makes the pair of alignment members 91 disposed opposite each other in the sheet width direction Dw align the sheet S in the sheet width direction Dw by making contact, from both sides in the sheet width direction Dw, the side edges of the sheet S conveyed along the sheet conveyance passage 45.

Next, as shown in FIG. 9 , the control portion 7 controls the contact-release mechanism 8 to bring the first and second conveyance rollers 4 a and 4 b constituting the pair of conveyance rollers 4 r near the alignment mechanism 9 into contact with each other with the sheet S nipped between them so as to hold the sheet S at the nip again. Then the control portion 7 restarts rotating the pair of conveyance rollers 4 r and restarts conveying the sheet S to the recording portion 5.

According to the configuration described above, skew correction for correcting a skew of the sheet S with respect to the sheet conveyance direction Dc and displacement correction for correcting a displacement of the sheet S in the sheet width direction Dw do not even require a detection portion with an expensive sensor such as a CIS sensor or the like. It is thus possible, with a low-cost configuration, to place the sheet S at an appropriate position in the sheet conveyance passage 45.

Using the driving motor 924 configured as a stepping motor as a driving source for moving each of the pair of alignment members 91 permits them to be moved independently of each other with different pulse numbers. Using the stepping motor helps increase resolution according to the drive reduction ratio and the motor's excitation type, and helps increase the movement accuracy of the pair of alignment members 91.

The driving motor 924 moves the pair of alignment members 91, which are disposed opposite each other in the sheet width direction Dw, individually in the sheet width direction Dw and this permits the sheet S to be aligned at a predetermined alignment position at each of one and the other sides in the sheet width direction Dw.

The urging members 925 urge the pair of alignment members 91, which are disposed opposite each other in the sheet width direction Dw, independently along the direction moving away from the sheet S, and this helps suppress a backlash when the alignment driving portion 92 moves the pair of alignment members 91. It is thus possible to improve the stopping accuracy of the pair of alignment members 91.

As shown in FIGS. 3, 5 and 6 , the sheet pressing portion 93 is disposed above the conveyance surface of the sheet conveyance passage 45, at one side in the sheet width direction Dw. The sheet pressing portion 93 includes a sheet pressing member 931, a guide member 932, a belt 933, a pair of pullies 934, and a driving motor 935.

The sheet pressing member 931 is attached to the one-side alignment members 91 r disposed at one side in the sheet width direction Dw out of the pair of alignment members 91 disposed side by side in the sheet width direction Dw. In this embodiment, the sheet width direction Dw coincides with the front-rear direction with respect to the inkjet recording apparatus 1 and the sheet pressing member 931 is attached to the one-side alignment members 91 r disposed at the rear side of the inkjet recording apparatus 1. The sheet pressing member 931 is attached to each of the two rear-side one-side alignment members 91 r disposed side by side along the sheet conveyance direction Dc. The sheet pressing member 931 includes a shaft 931 a and a pressing segment 931 b.

The shaft 931 a is located above the conveyance surface for the sheet S in the sheet conveyance passage 45. The shaft 931 a, has, for example, a cylindrical shape extending in the sheet width direction Dw and is supported by the one-side alignment members 91 r. The shaft 931 a is rotatable about an axis extending in the sheet width direction Dw.

The pressing segment 931 b is fixed to the shaft 931 a and extends outward in a radial direction of the shaft 931 a. As the shaft 931 a rotates about the axis extending in the sheet width direction Dw, the pressing segment 931 b moves into and out of the sheet conveyance passage 45 from and to above it. The pressing segment 931 b is formed of, for example, an elastic material such as rubber.

The guide member 932 has a rod-like shape extending in the sheet width direction Dw. The guide member 932 penetrates the alignment members 91 and the shaft 931 a of the sheet pressing member 931 in the sheet width direction Dw. The guide member 932 is attached to each of the two alignment members 91 disposed side by side along the sheet conveyance direction Dc. The alignment members 91 and the shaft 931 a can reciprocate in the extension direction of the guide member 932, that is, in the sheet width direction Dw. The shaft 931 a is rotatable, together with the guide member 932, about the axis extending to the sheet width direction Dw.

The belt 933 is an endless belt formed in an oval shape along the sheet conveyance direction Dc, in a direction orthogonal to the guide member 932. The belt 933 is wound around and supported by the pair of pullies 934. The belt 933 is rotated by the pair of pullies 934 and rotates the two guide members 932, which are disposed side by side along the sheet conveyance direction Dc, in the same direction and at the same speed.

The pair of putties 934 are disposed side by side along the sheet conveyance direction Dc. The putties 934 are attached to the apparatus main body 2 so as to be rotatable about a rotation axis extending in the sheet width direction Dw. The pair of pullies 934 each have the guide member 932 coaxially fixed to it. One of the pair of putties 934 is coupled to the driving motor 935 via a gear train and receives a rotative force from the driving motor 935. In this way, the pair of pullies 934 rotate the endless belt 933 wound around them and rotate the two guide members 932.

The driving motor 935 is connected to one of the pair of putties 934 and rotates the pullies 934. When the driving motor 935 is driven, the belt 933 rotates via the putties 934 and the two guide members 932 rotates about an axis extending in the sheet width direction Dw. In this way, the pressing segment 931 b on the sheet pressing member 931 moves into or out of the sheet conveyance passage 45 from or to above it. That is, the sheet pressing member 931 presses the upper surface of the sheet S at one side (rear side) in the sheet width direction Dw.

Next, the operation of the contact-release mechanism 8 and the alignment mechanism 9 when the sheet pressing member 931 is used will be described with reference to FIG. 7 , as well as FIGS. 10, 11, 12, and 13 . FIG. 10 is a schematic side view around the alignment mechanism 9 in FIG. 6 , showing a state where the pair of alignment members 91 are in contact with the sheet S when the sheet pressing member 931 is used. FIG. 11 is a schematic side view around the alignment mechanism 9 in FIG. 6 , showing a state where the sheet S is in contact with the sheet pressing member 931. FIG. 12 is a schematic side view around the alignment mechanism 9 in FIG. 6 , showing a state where only the other-side alignment member 91 f out of the pair of alignment members 91 is apart from the sheet S. FIG. 13 is a schematic side view around the alignment mechanism 9 in FIG. 6 , showing a state where the pressing of the sheet S by the sheet pressing member 931 is canceled.

As shown in FIG. 7 , before the sheet S reaches the alignment mechanism 9, the pair of alignment members 91 are on standby in a state where the interval between them in the sheet width direction Dw is longer than the width of the sheet S. The width of the sheet S is set previously based on the size of the sheet S stored in the sheet feed portion 3.

When the sheet S reaches the alignment mechanism 9, the control portion 7 stops the rotation of the pair of conveyance rollers 4 r to stop conveying the sheet S. As shown in FIG. 10 , the control portion 7 then controls the contact-release mechanism 8 to move away from each other the first and second conveyance rollers 4 a and 4 b constituting the pair of conveyance rollers 4 r near the alignment mechanism 9. The control portion 7 then aligns the sheet S with the two pairs of alignment members 91. As shown in FIG. 10 , meanwhile, the sheet S may curl in the sheet width direction Dw.

Next, as shown in FIG. 11 , the control portion 7 controls the sheet pressing portion 93 so that the sheet pressing member 931 presses the upper surface of the sheet S at one side (rear side) in the sheet width direction Dw. Specifically, with respect to the sheet S having reached the alignment mechanism 9, the sheet pressing portion 93 is controlled to rotate the guide member 932 so as to press the pressing segment 931 b on the sheet pressing member 931 against the upper surface of the sheet S from above. Meanwhile, the pressing segment 931 b is elastically deformed to nip and hold the sheet S between itself and the one-side alignment member 91 r in the up-down direction.

Next, as shown in FIG. 12 , the control portion 7 controls the alignment driving portion 92 to move the other-side alignment member 91 f disposed at the other side (front side) in the sheet width direction Dw away from the side edge of the sheet S.

Next, as shown in FIG. 13 , the control portion 7 controls the contact-release mechanism 8 to bring the first and second conveyance rollers 4 a and 4 b constituting the pair of conveyance rollers 4 r near the alignment mechanism 9 into contact with each other with the sheet S nipped between them so as to hold the sheet S at the nip again.

The control portion 7 further controls the sheet pressing portion 93 to cancel the pressing of the sheet S by the sheet pressing member 931. Specifically, the sheet pressing portion 93 is controlled to rotate the guide member 932 so as to move up the pressing segment 931 b on the sheet pressing member 931 in contact with the upper surface of the sheet S and thereby cancel the state in which the pressing segment 931 b pressed against the sheet S.

The control portion 7 restarts rotating the pair of conveyance rollers 4 r and restarts conveying the sheet S to the recording portion 5.

As shown in FIG. 10 , according to the configuration described above, if the sheet S curls in the sheet width direction Dw when the pair of alignment members 91 align the sheet S, it is possible to place the sheet S at an appropriate position in the sheet conveyance passage. It is thus possible to improve the positioning accuracy of the sheet S in the sheet conveyance passage 45.

FIG. 14 is a top view around an alignment mechanism 9 in a sheet conveyance device 4 in an inkjet recording apparatus 1 according to a second embodiment. The alignment mechanism 9 in the sheet conveyance device 4 in the inkjet recording apparatus 1 according to the second embodiment includes, as the pair of alignment members 91, a first alignment member 91C, a second alignment member 91D and a third alignment member 91E.

The first alignment member 91C is a one-side alignment member that is disposed at one side (rear side) in the sheet width direction Dw and that makes contact with the sheet S over an entire side edge of it from downstream to upstream in the sheet conveyance direction Dc. The second alignment member 91D is an other-side alignment member that is disposed at the other side (front side) in the sheet width direction Dw, downstream in the sheet conveyance direction Dc, opposite the first alignment members 91C in the sheet width direction Dw and that makes contact with the downstream side edge of the sheet S. The third alignment member 91E are an other-side alignment member disposed at the other side (front side) in the sheet width direction Dw, upstream in the sheet conveyance direction Dc, opposite the first alignment members 91C in the sheet width direction Dw and that makes contact with the upstream side edge of the sheet S.

Even with this configuration, skew correction for correcting a skew of the sheet S with respect to the sheet conveyance direction Dc and displacement correction for correcting a displacement of the sheet S in the sheet width direction Dw do not even require a detection portion with an expensive sensor such as a CIS sensor or the like. It is thus possible, with a low-cost configuration, to place the sheet S at an appropriate position in the sheet conveyance passage 45.

FIG. 15 is a schematic sectional view of an inkjet recording apparatus 1 according to a third embodiment. A sheet conveyance device 4 in the inkjet recording apparatus 1 according to the third embodiment includes a plurality of sheet conveyance passages.

The plurality of sheet conveyance passages include a feeding sheet conveyance passage 46 and a duplex sheet conveyance passage 47. The feeding sheet conveyance passage 46 extends from a sheet feed portion 3 storing a sheet S to a recording portion 5 which records an image to the sheet S. The duplex sheet conveyance passage 47 conveys the sheet S having the image recorded to it at the recording portion 5 once again to the recording portion 5.

The plurality of sheet conveyance passages each include a pair of conveyance rollers 4 r, a contact-release mechanism 8, and an alignment mechanism 9. According to this configuration, in either of the feeding sheet conveyance passage 46 for simplex recording and the duplex sheet conveyance passage 47 for duplex recording, skew correction and displacement correction do not even require a detection portion with an expensive sensor such as a CIS sensor or the like. It is thus possible, with a low-cost configuration, in both simplex and duplex recording, to place the sheet S at an appropriate position in the feeding and duplex sheet conveyance passages 46 and 47.

FIG. 16 is a diagram showing the timing of sheet conveyance and alignment on the inkjet recording apparatus 1. With one sheet conveyance passage alone, for example, alignment of the first sheet S in the sheet width direction Dw has to be performed during a sheet interval T1, which is relatively short compared with the passage time of the first and second sheets S entering the recording portion 5. As a result, as the conveying of the sheet S is sped up and the productivity of image recording is increased, it may be difficult to place the sheet S at the appropriate position in the sheet conveyance passage.

By contrast, with two sheet conveyance passages, the sheet S passes the first and second sheet conveyance passages in this order; thus for example, alignment of the first sheet S in the sheet width direction Dw can be performed during a sheet interval T2, which is relatively long compared with the passage time of the first and third sheets S entering the recording portion 5. As a result, even as the conveying of the sheet S is sped up, it is easy to place the sheet S at the appropriate position in the sheet conveyance passage.

The feeding sheet conveyance passage 46 includes a first sheet conveyance passage 461 and a second sheet conveyance passage 462. The first and second conveyance passage 461 and 462 are disposed side by side in the sheet conveyance direction and the sheet S is selectively conveyed. Specifically, the feeding sheet conveyance passage 46 extends from the sheet feed portion 3 first along a single passage, then branches midway into the first and second conveyance passage 461 and 462, which finally meet just short of the recording potion 5. The first and second sheet conveyance passages 461 and 462 each include the pair of conveyance rollers 4 r, the contact-release mechanism 8, and the alignment mechanism 9.

According to this configuration, for example, owing to the provision of two sheet conveyance passages, even with a configuration with increased productivity of image recording, there is no need for a detection portion with an expensive sensor. It is thus possible, with a low-cost and highly-productive configuration, to place the sheet S at an appropriate position in the sheet conveyance passage 46.

The second sheet conveyance passage 462 and the duplex sheet conveyance passage 47 meet at a confluence portion 48 downstream in the sheet conveyance direction to reach the recording portion 5. The alignment mechanism 9 is disposed in the confluence portion 48 where the second sheet conveyance passage 462 and the duplex sheet conveyance passage 47 meet. The alignment mechanism 9 is thus shared between the second sheet conveyance passage 462 and the duplex sheet conveyance passage 47. According to this configuration, it is possible to reduce the number of alignment mechanisms 9 and thus to further reduce the cost of the apparatus.

As described above, the inkjet recording apparatus 1 includes the sheet conveyance device 4 configured as described above and the recording portion (image forming portion) 5 which forms an image on the sheet S conveyed by the sheet conveyance device 4. The alignment mechanism 9 is disposed closely upstream of the recording portion 5 in the sheet conveyance direction; thus on the inkjet recording apparatus 1, skew correction and displacement correction of the sheet S do not even require a detection portion with an expensive sensor. It is thus possible, on the low-cost inkjet recording apparatus 1, to place the sheet S at an appropriate position in the sheet conveyance passage 45.

While an embodiment of the present disclosure has been described above, it is not meant to limit the scope of the present disclosure, which thus encompasses any modifications made without departure from the scope and sense equivalent to those claims.

For example, while, in the present disclosure, an inkjet recording apparatus 1 is described as one example of an image forming apparatus, an image forming apparatus is not limited to such an apparatus. An image forming apparatus according to the present disclosure can be an electrophotographic image forming apparatus which forms a toner image on a sheet. 

What is claimed is:
 1. A sheet conveyance device, comprising: a pair of conveyance rollers which conveys a sheet along a sheet conveyance passage; a contact-release mechanism which moves first and second conveyance rollers, constituting the pair of conveyance rollers, into contact with and away from each other; an alignment mechanism which aligns the sheet conveyed along the sheet conveyance passage at a predetermined alignment position in a sheet width direction orthogonal to the sheet conveyance direction; and a control portion which controls the pair of conveyance rollers, the contact-release mechanism, and the alignment mechanism, wherein the alignment mechanism includes a pair of alignment members movable toward and away from each other in the sheet width direction, the alignment members aligning the sheet in the sheet width direction by making contact, from both sides in the sheet width direction, with side edges of the sheet conveyed along the sheet conveyance passage, and the control portion controls the contact-release mechanism to move the first and second conveyance rollers away from each other, and aligns the sheet with the pair of alignment members located opposite each other in the sheet width direction.
 2. The sheet conveyance device according to claim 1, wherein the pair of alignment members include: a first pair of alignment members disposed downstream in the sheet conveyance direction, located opposite each other in the sheet width direction and making contact, from both sides in the sheet width direction, with downstream side edges of the sheet, and a second pair of alignment members disposed upstream in the sheet conveyance direction, located opposite each other in the sheet width direction and making contact, from both sides in the sheet width direction, with upstream side edges of the sheet.
 3. The sheet conveyance device according to claim 1, wherein the pair of alignment members include: a first alignment member disposed at one side in the sheet width direction and making contact with a side edge of the sheet, a second alignment member disposed at another side in the sheet width direction, downstream in the sheet conveyance direction, opposite the first alignment member in the sheet width direction, the second alignment member making contact with a downstream side edge of the sheet, a third alignment member disposed at another side in the sheet width direction, upstream in the sheet conveyance direction, opposite the first alignment member in the sheet width direction, the third alignment member making contact with an upstream side edge of the sheet.
 4. The sheet conveyance device according to claim 1, further comprising: driving motors which move the pair of alignment members located opposite each other in the sheet width direction independently of each other in the sheet width direction, and urging members which urge the pair of alignment members located opposite each other in the sheet width direction independently of each other in a direction away from the sheet.
 5. The sheet conveyance device according to claim 4, wherein the pair of alignment member includes a one-side alignment member disposed at the one side in the sheet width direction, and an other-side alignment member disposed at the other side in the sheet width direction, the alignment mechanism further includes a sheet pressing member which is attached to the one-end side aligning member and is configured to press an upper surface of the sheet at the one side in the sheet width direction, and the control portion, after controlling the alignment mechanism to align the sheet, controls the sheet pressing member to press the sheet at the one side in the sheet width direction, moves the other-side alignment member away from a side edge of the sheet, controls the contact-release mechanism to move the first and second conveyance rollers into contact with each other, and cancels pressing of the sheet by the sheet pressing member.
 6. The sheet conveyance device according to claim 1, wherein the sheet conveyance passage includes a plurality of the sheet conveyance passages, and the plurality of the sheet conveyance passages each include the pair of conveyance rollers, the contact-release mechanism, and the alignment mechanism.
 7. The sheet conveyance device according to claim 6, wherein the plurality of sheet conveyance passages include: a feeding sheet conveyance passage which extends from a sheet feed portion which stores the sheet to a recording portion which records an image to the sheet, and a duplex sheet conveyance passage which conveys the sheet having the image recorded thereto at the recording portion once again to the recording portion.
 8. The sheet conveyance device according to claim 7, wherein the feeding sheet conveyance passage includes a first sheet conveyance passage and a second conveyance passage which are disposed side by side in the sheet conveyance direction and along which the sheet is selectively conveyed.
 9. The sheet conveyance device according to claim 8, wherein the second sheet conveyance passage and the duplex sheet conveyance passage meet at a confluence portion downstream in the sheet conveyance direction, and the alignment portion is disposed in the confluence portion.
 10. An image forming apparatus, comprising: the sheet conveyance device according to claim 1, and an image forming portion which forms an image on the sheet conveyed by the sheet conveyance device, wherein the alignment portion is disposed closely upstream of the image forming portion in the sheet conveyance direction. 